[(1R,2R,4aS,8aS)-2-Hydroxy-2,5,5,8a-tetramethyldecahydronaphthalen-1-yl]acetic acid, from now on referred to also as (2R)-hydroxy-acid, may be a useful precursor of (+)-sclareolide, an intermediate in the synthesis of the perfumery ingredient (−)-Ambroxe®.
Despite this fact, only few processes for the preparation of (2R)-hydroxy-acid, or a salt thereof, by optical resolution of a racemic [(1RS,2RS,4aSR,8aSR)-2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalen-1-yl]acetic acid, from now on referred to also as (2RS)-hydroxy-acid, or a salt thereof, have been reported in the prior art.
In EP 550 889 is reported a process for the optical resolution of (2RS)-hydroxy-acid in which a 1-(aryl)ethylamine is used as resolving agent. For the same process, but using the sodium salt of (2RS)-hydroxy-acid as starting material, Koga et al. in Tetrahedron Asymmetry, (1998), 9, 3819, report the use as resolving agent of some 1,2- or 1,3-amino-alcohols in addition to the previously cited 1-(aryl)ethylamine.
However, all the prior art procedures suffer from the disadvantages of needing complex procedures implying slow and complicated crystallization procedures and/or a re-crystallization. Consequently, low yields of the final product are frequently, if not always, observed.
Therefore, there is a need for a process capable of providing an optically active enantiomer of a (2RS)-hydroxy-acid, or a salt thereof, and being of improved efficiency.